TCO-PEG4-NHS ester

This TCO-PEG4-NHS ester is a bifunctional PROTAC linker designed to couple a trans-cyclooctene (TCO) moiety to amine-containing ligands through an NHS-activated ester. Its PEG-based spacer improves solubility and provides conformational flexibility, which can enhance productive ternary complex formation in targeted protein degradation workflows. The following sections describe the linker’s structure and the practical reactivity considerations for PROTAC assembly in detail below.

Structure: The molecule contains a PEG-based spacer terminating in an NHS ester for acyl transfer to nucleophiles, and a TCO functional group suitable for bioorthogonal inverse-electron-demand cycloaddition. It comprises an activated carboxylate, ether-rich repeating units, and a strained alkene within the TCO scaffold, supporting water-compatible handling.

Reactivity: The NHS ester reacts with primary amines via nucleophilic acyl substitution, typically under mild aqueous buffer conditions that preserve NHS reactivity. For PROTAC construction, amine-bearing ligands are coupled first to form stable amide bonds, followed by TCO-mediated conjugation to complementary partners using strain-promoted cycloaddition principles. Use freshly prepared solutions, avoid primary amine-containing buffers, and consider standard coupling additives only when compatible with NHS ester chemistry.